The invention relates to a display device, and in particular to a display panel having a display mode and an input mode employed in a display device.
As electronic commerce has created and the transmission rate of information exchange has increased, conventional input interfaces, such as keyboards and mice, cannot adequately satisfy the requirement for rapid data transmission. Thus, new modes of inputting information, such as vocal voice and handwritten input, may replace conventional input interfaces. An alternative input interface is the touch panel developed.
In the prior art of touch panels, since leakage current of amorphous silicon thin film transistors (a-Si TFTs) is sensitive to light, a-Si TFTs are used to form photodiodes serving as image sensors. Jeong Hyun Kim of LG. Philips LCD Co. discloses a fingerprint scanner, in which a photodiode formed by an a-Si TFT senses the light reflected by a finger, and then a readout amplifier determines a fingerprint.
Moreover, T.Nakamura of Toshiba Matsushita Display discloses a TFT-LCD with image capture function using LTPS technology, in which a low temperature poly-silicon (LTPS) TFT serves as a light sensor. In the TFT-LCD of T.Nakamura, light from a backlight source is transmitted to an object through a pixel unit, and an LTPS TFT senses the light reflected from the object, resulting in the discharge of a storage capacitor within the pixel unit. Finally the image of the object is determined according to the charges in the storage capacitor.